Image sensors and methods of forming the same

ABSTRACT

An image sensor includes a substrate including a light-receiving region and a light-shielding region, a device isolation pattern in the substrate of the light-receiving region to define active pixels, and a device isolation region in the substrate of the light-shielding region to define reference pixels. An isolation technique of the device isolation pattern is different from that of the device isolation region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/994,330, filed Jan. 31, 2016, which claims the benefit of priorityunder 35 U.S.C. §119 from Korean Patent Application No. 10-2015-0006011,filed on Jan. 13, 2015, in the Korean Intellectual Property Office(KIPO), the entire contents of each of which are incorporated herein byreference.

BACKGROUND

The inventive concepts relate to image sensors including deviceisolation patterns and/or methods of forming the same.

An image sensor is a semiconductor device that converts an optical imageinto electrical signals. Image sensors may be categorized as any one ofcharge coupled device (CCD)-type image sensors and complementarymetal-oxide-semiconductor (CMOS)-type image sensors. CIS is short forthe CMOS-type image sensor. The CIS may include a plurality of pixelstwo-dimensionally arranged, and each of the pixels may include aphotodiode (PD). The photodiode may convert incident light into anelectrical signal.

SUMMARY

Example embodiments of the inventive concepts may provide image sensorscapable of improving optical characteristics and methods of forming thesame.

In at least one example embodiment, an image sensor may include asubstrate including a light-receiving region and a light-shieldingregion, a device isolation pattern in the substrate of thelight-receiving region configured to define active pixels, and a deviceisolation region in the substrate of the light-shielding regionconfigured to define reference pixels. The device isolation pattern mayinclude a different material from the device isolation region.

In at least one example embodiment, the device isolation pattern mayinclude an insulating material filling a trench in the substrate.

In at least one example embodiment, the device isolation pattern mayinclude a first device isolation pattern in the light-receiving region,and a second device isolation pattern between the reference pixels inthe light-shielding region. A shape of the second device isolationpattern may be different from a shape of the first device isolationpattern.

In at least one example embodiment, the device isolation region may be adopant region formed by doping a portion of the substrate with dopants.

In at least one example embodiment, the image sensor may further includea photoelectric conversion part in the substrate of each of the activepixels and the reference pixels.

In at least one example embodiment, structures of the photoelectricconversion parts in the reference pixels may be the same as orsymmetrical to those of the photoelectric conversion parts in the activepixels.

In at least one example embodiment, the device isolation pattern mayinclude a material of which a refractive index is lower than that of thesubstrate.

In at least one example embodiment, the substrate may further include adummy region between the light-receiving region and the light-shieldingregion. The dummy region may have a plurality of dummy pixels.

In at least one example embodiment, the device isolation region may befurther in the dummy region to define the dummy pixels.

In at least one example embodiment, the device isolation pattern mayinclude a first device isolation pattern in the light-receiving region,and a second device isolation pattern between the dummy pixels in thedummy region. A shape of the second device isolation pattern may bedifferent from a shape of the first device isolation pattern.

In at least one example embodiment, an Image sensor may include asubstrate including active pixels and reference pixels. The activepixels may be defined by a device isolation pattern filling a trenchformed in the substrate, and the reference pixels may be defined by adopant region formed by doping a portion of the substrate with dopants.

In at least one example embodiment, the image sensor may further includea photoelectric conversion part in the substrate of each of the activepixels and the reference pixels.

In at least one example embodiment, the photoelectric conversion partsmay be adjacent to a first surface of the substrate, and the trench mayextend from a second surface of the substrate into the substrate. Thesecond surface may be opposite to the first surface.

In at least one example embodiment, the image sensor may further includea shallow device isolation layerin the substrate to define activeregions. The shallow device isolation layer may be adjacent to the firstsurface of the substrate.

In at least one example embodiment, the image sensor may further includetransfer gates on the first surface of the substrate and on thephotoelectric conversion parts, respectively, an interconnectionstructure covering the transfer gates on the first surface of thesubstrate, and a color filter and a micro-lens on the second surface ofthe substrate of each of the active pixels.

In at least one example embodiment, the dopant region may be doped withdopants of a first conductivity type, and the photoelectric conversionparts may be doped with dopants of a second conductivity type differentfrom the first conductivity type.

In at least one example embodiment, the reference pixels may have thesame shape and the same area as the active pixels when viewed from aplan view.

In at least one example embodiment, the image sensor may further includea light-shielding pattern on the substrate to cover the referencepixels. The active pixels may be exposed by the light-shielding pattern.

In at least one example embodiment, a method of forming an image sensormay include providing a substrate including a light-receiving region anda light-shielding region, injecting dopants into the substrate to form adevice isolation region defining reference pixels in the light-shieldingregion, etching the substrate to form a trench in the light-receivingregion, and forming a device isolation pattern in the trench to defineactive pixels in the light-receiving region.

In at least one example embodiment, injecting the dopants into thesubstrate may be performed on a first surface of the substrate, andetching the substrate may be performed on a second surface of thesubstrate. The second surface may be opposite to the first surface.

In at least one example embodiment, the substrate of the light-shieldingregion may not be exposed when the trench is formed.

In at least one example embodiment, the method may further includeperforming a doping process on the first surface of the substrate toform photoelectric conversion parts in the substrate. The photoelectricconversion parts may be formed in the active and reference pixels,respectively.

In at least one example embodiment, a method of forming an image sensorincludes injecting dopants into a substrate to form a device isolationregion, the device isolation region defining reference pixels, etchingthe substrate to form a trench, and forming a device isolation patternin the trench to define active pixels. The injecting dopants into thesubstrate may include injecting dopants on at least one of a firstsurface of the substrate and a second surface of the substrate. Thesecond surface is opposite to the first surface. The substrate is notexposed when the trench is formed. The method may also includeperforming a doping process on the first surface of the substrate toform photoelectric conversion parts in the substrate. The photoelectricconversion parts may be formed in the active and reference pixels,respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the non-limiting embodimentsherein may become more apparent upon review of the detailed descriptionin conjunction with the accompanying drawings. The accompanying drawingsare merely provided for illustrative purposes and should not beinterpreted to limit the scope of the claims. The accompanying drawingsare not to be considered as drawn to scale unless explicitly noted. Forpurposes of clarity, various dimensions of the drawings may have beenexaggerated.

FIG. 1 is a schematic block diagram illustrating an image sensoraccording to at least one example embodiment of the inventive concepts.

FIG. 2 is a schematic circuit diagram illustrating a sensor array of animage sensor according to at least one example embodiment of theinventive concepts.

FIG. 3 is a circuit diagram illustrating a unit pixel of an image sensoraccording to at least one example embodiment of the inventive concepts.

FIGS. 4A and 4B are schematic plan views illustrating image sensorsaccording to at least one example embodiment of the inventive concepts.

FIG. 5A is an enlarged plan view of a region ‘I’ of FIG. 4A toillustrate an image sensor according to at least one example embodimentof the inventive concepts.

FIG. 5B is a cross-sectional view taken along a line V-V of FIG. 5A.

FIG. 6A is a plan view illustrating an image sensor according to atleast one example embodiment of the inventive concepts.

FIG. 6B is a cross-sectional view taken along a line VI-VI of FIG. 6A.

FIG. 7A is a plan view illustrating an image sensor according to atleast one example embodiment of the inventive concepts.

FIG. 7B is a cross-sectional view taken along a line VII-VII of FIG. 7A.

FIG. 8A is a plan view illustrating an image sensor according to atleast one example embodiment of the inventive concepts.

FIG. 8B is a cross-sectional view taken along a line VIII-VIII of FIG.8A.

FIG. 9A is a plan view illustrating an image sensor according to atleast one example embodiment of the inventive concepts.

FIG. 9B is a cross-sectional view taken along a line IX-IX of FIG. 9A.

FIG. 10A is a plan view illustrating an image sensor according to atleast one example embodiment of the inventive concepts.

FIG. 10B is a cross-sectional view taken along a line X-X of FIG. 10A.

FIGS. 11A to 11D are cross-sectional views illustrating a method offorming an image sensor according to at least one example embodiment ofthe inventive concepts.

FIG. 12A is a schematic block diagram illustrating a processor-basedsystem implemented with an image sensor according to at least oneexample embodiment of the inventive concepts. FIG. 12B illustrates anelectronic device implemented with an image sensor according to at leastone example embodiment of the inventive concepts.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It should be understood that when an element or layer is referred to asbeing “on,” “connected to,” “coupled to,” or “covering” another elementor layer, it may be directly on, connected to, coupled to, or coveringthe other element or layer or intervening elements or layers may bepresent. In contrast, when an element is referred to as being “directlyon,” “directly connected to,” or “directly coupled to” another elementor layer, there are no intervening elements or layers present. Likenumbers refer to like elements throughout the specification. As usedherein, the term “and/or” includes any and all combinations of one ormore of the associated listed items.

It should be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Theseterms are only used to distinguish one element, component, region,layer, or section from another region, layer, or section. Thus, a firstelement, component, region, layer, or section discussed below could betermed a second element, component, region, layer, or section withoutdeparting from the teachings of example embodiments.

Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,”“upper,” and the like) may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It should be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” may encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The terminology used herein is for the purpose of describing variousembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“includes,” “including,” “comprises,” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the shapes of regions illustrated herein but are to includedeviations in shapes that result, for example, from manufacturing. Theregions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the actual shape of a region of adevice and are not intended to limit the scope of example embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, including those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

Although corresponding plan views and/or perspective views of somecross-sectional view(s) may not be shown, the cross-sectional view(s) ofdevice structures illustrated herein provide support for a plurality ofdevice structures that extend along two different directions as would beillustrated in a plan view, and/or in three different directions aswould be illustrated in a perspective view. The two different directionsmay or may not be orthogonal to each other. The three differentdirections may include a third direction that may be orthogonal to thetwo different directions. The plurality of device structures may beintegrated in a same electronic device. For example, when a devicestructure (e.g., a memory cell structure or a transistor structure) isillustrated in a cross-sectional view, an electronic device may includea plurality of the device structures (e.g., memory cell structures ortransistor structures), as would be illustrated by a plan view of theelectronic device. The plurality of device structures may be arranged inan array and/or in a two-dimensional pattern.

FIG. 1 is a schematic block diagram illustrating an image sensoraccording to at least one example embodiment of the inventive concepts.FIG. 2 is a schematic circuit diagram illustrating a sensor array of animage sensor according to at least one example embodiment of theinventive concepts.

Referring to FIG. 1, an image sensor according to at least one exampleembodiment of the inventive concepts may include an active pixel sensor(APS) array 10, a row decoder 20, a row driver 30, a column decoder 40,a timing generator 50, a correlated double sampler (CDS) 60, ananalog-to-digital converter (ADC) 70, and an input/output (I/O) buffer80.

As shown in FIG. 2, the APS array 10 may include a light-receivingregion 110 and a light-shielding region 120, and may includetwo-dimensionally arranged unit pixels. Light may be incident on thelight-receiving region 110, but may not be incident on thelight-shielding region 120. The unit pixels may include active pixels APand reference pixels RP. The active pixels AP may be in thelight-receiving region 110, and may convert the incident light intoelectrical signals. The reference pixels RP may be in thelight-shielding region 120, and may generate an electrical signal thatoccurs in a unit pixel on which light is not incident. The unit pixelsof the light-receiving region 110 and the light-shielding region 120 maybe driven by a plurality of driving signals (e.g., a row selectionsignal Row SEL, a reset signal Rx, and a charge transfer signal Tx),which are provided from the row driver 30 (shown in FIG. 1). Inaddition, electrical signals generated in the APS array 10 may beprovided to the correlated double sampler 60.

As shown in FIG. 1, the row driver 30 may provide the plurality ofdriving signals for driving the unit pixels to the APS array 10 inresponse to resultant signals decoded in the row decoder 20. If the unitpixels are arranged in a matrix form, the row driver 30 may provide thedriving signals to the unit pixels of each of rows.

The timing generator 50 may provide a timing signal and a control signalto the row decoder 20 and the column decoder 40.

The correlated double sampler 60 may receive the electrical signalsgenerated from the APS array 10, and may hold and sample the receivedelectrical signals. The correlated double sampler 60 may sample both aspecific noise level and a signal level by the electrical signal tooutput a difference level corresponding to a difference between thenoise level and the signal level.

The analog-to-digital converter 70 may convert an analog signalcorresponding to the difference level provided from the correlateddouble sampler 60 into a digital signal and may output the converteddigital signal.

The I/O buffer 80 may latch the digital signals, and the latched signalsmay be sequentially transmitted to an image signal treatment part (notshown) in response to a resultant signal decoded in the column decoder40.

FIG. 3 is a circuit diagram illustrating a unit pixel of an image sensoraccording to at least one example embodiment of the inventive concepts.

Referring to FIG. 3, each of the unit pixels AP and RP may include aphotoelectric conversion part PD converting incident light into anelectrical signal and sensing elements sensing the electrical signalgenerated in the photoelectric conversion part PD. The sensing elementsmay include a transfer element TA, a reset element RG, a driver elementDG, and a selection element SG. The driving signals Tx, Rx and Row SELof the transfer element TA, the reset element RG, and the selectionelement SG may be applied in common to the unit pixels of the same row.In at least one example embodiment, the transfer element TA, the resetelement RG, the driver element DG, and the selection element SG may befield effect transistors.

The photoelectric conversion part PD may generate and accumulate chargescorresponding to the incident light. In at least one example embodiment,the photoelectric conversion part PD may include at least one of aphotodiode, a photo transistor, a photo gate, or a pinned photodiode(PPD). The photoelectric conversion part PD may be connected to thetransfer element TA used to transfer the accumulated charges to afloating diffusion region FD.

The floating diffusion region FD may receive the charges accumulated inthe photoelectric conversion part PD. The floating diffusion region FDmay have a parasitic capacitance, so the charges may be accumulativelystored in the floating diffusion region FD. In addition, the floatingdiffusion region FD may be electrically connected to the driver elementDG to control the driver element DG.

The transfer element TA may transfer the charges from the photoelectricconversion part PD to the floating diffusion region FD. The transferelement TA may generally consist of one element and may be controlled bythe transfer signal Tx.

The reset element RG may periodically reset the floating diffusionregion FD and may be controlled by the reset signal Rx. A source of thereset element RG may be connected to the floating diffusion region FD,and a drain of the reset element RG may be connected to a power voltageVDD. Thus, if the reset element RG is turned on by the reset signal Rx,the power voltage VDD connected to the drain of the reset element RG maybe transferred to the floating diffusion region FD.

The driver element DG may be coupled to a constant-current source (notshown) to act as a source follower buffer amplifier. The driver elementDG may amplify a variation in an electrical potential of the floatingdiffusion region FD receiving the photo charges from the photoelectricconversion part PD and may output the amplified variation in theelectrical potential to an output line V out.

The selection element SG may select the unit pixels of a selected row.The selection element SG may be driven by the row selection signal RowSEL. If the selection element SG is turned on, the power voltage VDDconnected to a drain of the selection element SG may be transferred tothe drain of the driver element DG.

According to at least one example embodiment as illustrated in FIG. 3,the unit pixel may have a four-element structure including fourelements. However, the inventive concepts are not limited thereto. In atleast one example embodiment, the unit pixel may have a three-elementstructure including three elements, a five-element structure includingfive elements, or a photo gate structure similar to the four-elementstructure. In at least one example embodiment, the unit pixels may shareat least one of the elements.

Hereinafter, image sensors according to at least one example embodimentof the inventive concepts will be described in detail.

FIGS. 4A and 4B are schematic plan views illustrating image sensorsaccording to at least one example embodiment of the inventive concepts.

Referring to FIGS. 4A and 4B, an image sensor may include the APS array10 (shown in FIG. 1) including the light-receiving region 110, thelight-shielding region 120, and pad region 130.

As described with reference to FIG. 2, a plurality of unit pixels may bearranged in a matrix form in the APS array 10. Electrical signalsgenerated by incident light may be provided from the APS array 10. Thepad region 130 may include conductive pads that are used to transmitcontrol signals to the APS array 10 and/or to receive photoelectricsignals from the APS array 10. The pad region 130 may be around the APSarray 10 so as to be easily connected to an external system. In otherwords, the pad region 130 may correspond to an edge portion of the imagesensor.

The APS array 10 in which the unit pixels are arranged may include thelight-receiving region 110 and the light-shielding region 120. The lightmay be incident on the light-receiving region 110, but may not beincident on the light-shielding region 120. According to exampleembodiment, the light-shielding region 120 may be between thelight-receiving region 110 and the pad region 130. In at least oneexample embodiment, the light-shielding region 120 may be around thelight-receiving region 110, as illustrated in FIG. 4A. Alternatively,the light-shielding region 120 may be at a side of the light-receivingregion 110, as illustrated in FIG. 4B. However, example embodiments ofthe inventive concepts are not limited thereto. In at least one exampleembodiment, the positions of the light-receiving region 110 may bemodified.

FIG. 5A is an enlarged plan view of a region ‘I’ of FIG. 4A, whichillustrates an image sensor according to at least one example embodimentof the inventive concepts. FIG. 5B is a cross-sectional view taken alonga line V-V′ of FIG. 5A. Hereinafter, the descriptions mentioned abovewill be omitted or mentioned briefly to avoid duplication ofexplanation.

Referring to FIGS. 5A and 5B, an image sensor 1 may include a substrate100 having a light-receiving region 110, a light-shielding region 120, adevice isolation pattern 200, photoelectric conversion parts PD,transfer gates TG, and a light-shielding pattern 520. Thelight-shielding region 120 may be covered with the light-shieldingpattern 520. The substrate 100 may have a first surface 100 a and asecond surface 100 b that are opposite to each other. The first surface100 a may correspond to a front side of the substrate 100, and thesecond surface 100 b may correspond to a back side of the substrate 100.In at least one example embodiment, the substrate 100 may be asemiconductor substrate (e.g., a silicon substrate, a germaniumsubstrate, a silicon-germanium substrate, a II-VI group compoundsemiconductor substrate, a III-V group compound semiconductor substrate,or a silicon-on-insulator (SOI) substrate).

The light-receiving region 110 and the light-shielding region 120 may bedefined by the device isolation pattern 200. The device isolationpattern 200 may also be in the light-receiving region 110 to defineactive pixels AP. The device isolation pattern 200 may have a depth ofabout 0.3 mm to about 6 μm. The device isolation pattern 200 may bespaced apart from the first surface 100 a of the substrate 100. In atleast one example embodiment, the device isolation pattern 200 maypenetrate the substrate 100 so as to be exposed at the first and secondsurfaces 100 a and 100 b. In at least one example embodiment, the deviceisolation pattern 200 may extend onto the second surface 100 b of thesubstrate 100 to cover the second surface 100 b. According to at leastone example embodiment, as shown in FIG. 5B, the device isolationpattern 200 may not extend into and/or between reference pixels RP ofthe light-shielding region 120.

The device isolation pattern 200 may be a deep-trench isolation pattern.In at least one example embodiment, the device isolation pattern 200 mayinclude an insulating material that fills a trench 201 recessed from thesecond surface 100 b of the substrate 100. A width of a top surface ofthe device isolation pattern 200 may be wider than that of a bottomsurface of the device isolation pattern 200. Here, the top surface ofthe device isolation pattern 200 may be adjacent to the second surface100 b of the substrate 100, and the bottom surface of the deviceisolation pattern 200 may be adjacent to the first surface 100 a of thesubstrate 100. The device isolation pattern 200 may include at least oneof, but not limited to, silicon oxide, silicon nitride, or siliconoxynitride. The device isolation pattern 200 may include a singleinsulating layer or a plurality of insulating layers. The deviceisolation pattern 200 may include a material of which a refractive indexis lower than that of the substrate 100, so crosstalk between the activepixels AP may be minimized and/or prevented.

The active pixels AP may output electrical signals (e.g., photoelectricsignals) generated by the incident light. Defects (e.g., dangling bonds)caused by etch stress may occur at an interface between the deviceisolation pattern 200 and the substrate 100. A liner (not shown) or adoped region (not shown), which is used to cure the interface defectsbetween the device isolation pattern 200 and the substrate 100, may notbe provided. In this case, the charges may be generated by heat as wellas the incident light because of the interface defects between thedevice isolation pattern 200 and the substrate 100. The chargesgenerated by the interface defects may be transferred to thephotoelectric conversion part PD to generate a dark current. The activepixel AP may output an electrical signal (e.g., a noise signal)generated by the charges caused by the heat, as well as thephotoelectric signal. The noise signal occurring in the active pixel APmay include a signal generated by the dark current.

A device isolation region 300 may be in the light-shielding region 120of the substrate 100 to define the reference pixels RP. As illustratedin FIG. 5A, the reference pixels RP may have the same planar area andthe same volume as the active pixels AP. The device isolation region300, shown in FIG. 5B, may include a different material from the deviceisolation pattern 200. The light may not be incident on thelight-shielding region 120, so optical crosstalk may not occur betweenthe reference pixels RP. The reference pixels RP may not output thephotoelectric signal. In at least one example embodiment, the referencepixels RP may not output the photoelectric signal but may output onlyelectrical signals (e.g., noise signals) generated by charges caused byheat.

A method of isolating the reference pixels RP by the device isolationregion 300 may be different from the method of isolating the activepixels AP by the device isolation pattern 200. For example, the deviceisolation region 300 may define the reference pixels RP by a junctionisolation technique. The device isolation region 300 may be a dopantregion formed in the substrate 100. The device isolation region 300 maybe doped with dopants of a different conductivity type from dopants ofthe photoelectric conversion part PD. For example, the device isolationregion 300 may be doped with dopants of a first conductivity type (e.g.,P-type dopants). Since the device isolation region 300 includes thedopant region, interface defects may not occur between the deviceisolation region 300 and the substrate 100. The reference pixels RP maybe defined by the device isolation region 300 instead of the deviceisolation pattern 200, so the dark current may be reduced or preventedin the reference pixels RP. In other words, the mean value (e.g., areference signal) of electrical signals generated from the referencepixels RP may not include the noise signal generated by the darkcurrent. The noise signal, generated by the dark current, of theelectrical signal occurring in the active pixel AP may be removed usingthe reference signal. As described above, the dark current of the activepixel AP may occur by the interface defects between the device isolationpattern 200 and the substrate 100. As a result, even though the linerlayer (not shown) or the doped region (not shown) is not formed at theinterface between the device isolation pattern 200 and the substrate100, the image sensor 1 may output the electrical signal from which thenoise signal by the dark current is removed. In other words, opticalcharacteristics of the image sensor 1 may be improved.

The photoelectric conversion part PD may be formed in the substrate 100of each of the active and reference pixels AP and RP. The photoelectricconversion part PD in each of the reference pixels RP may be thesubstantially same as the photoelectric conversion part PD in each ofthe active pixels AP. For example, a structure, a shape and a positionof the photoelectric conversion part PD in the reference pixel RP may bethe same as or symmetrical to those of the photoelectric conversion partPD in the reference pixel RP. The photoelectric conversion part PD inthe reference pixel RP may include the same material as thephotoelectric conversion part PD in the reference pixel RP. Thephotoelectric conversion part PD may be a dopant region that is dopedwith dopants of a second conductivity type in the substrate 100. Forexample, the dopants of the second conductivity type may be N-typedopants. Here, the second conductivity type may be different from thefirst conductivity type of the device isolation region 300. Thephotoelectric conversion part PD may include a well region PW. The wellregion PW may be doped with dopants of the first conductivity type,e.g., P-type dopants. The well region PW may be adjacent to the firstsurface 100 a of the substrate 100.

A transfer gate TG and at least one element 150 may be on each of theactive and reference pixels AP and RP of the substrate 100. The transfergate TG may correspond to a gate of the transfer element TA illustratedin FIG. 3. In at least one example embodiment, the transfer gate TG mayhave a flat-type structure that is on the first surface 100 a of thesubstrate 100. Alternatively, the transfer gate TG may have aburied-type structure that extends from the surface 100 a of thesubstrate 100 into the substrate 100. The structure of the transfer gateTG on the reference pixel RP may be the same as and/or symmetrical tothat of the transfer gate TG on the active pixel AP. The at least oneelement 150 may correspond to at least one of the reset element RG, thedriver element DG, and the selection element SG (shown in FIG. 3). Agate insulating layer 160 may be between the substrate 100 and thetransfer gate TG.

A shallow device isolation layer STI may be on the first surface 100 aof the substrate 100. The shallow device isolation layer STI may includeat least one of silicon oxide, silicon nitride, and silicon oxynitride.The shallow device isolation layer STI may be shallower than the deviceisolation pattern 200. As illustrated in FIG. 5A, the shallow deviceisolation layer STI may define an active region in each of the activeand reference pixels AP and RP. The active region may include a regionused to operate the transfer gate TG and the element 150. For example,the active region may include a floating diffusion region FD andsource/drain regions SDR, as illustrated in FIG. 5B. The floatingdiffusion region FD and the source/drain regions SDR may be in thesubstrate 100 of each of the active and reference pixels AP and RP andmay be adjacent to the first surface 100 a of the substrate 100. Thesource/drain regions SDR may correspond to a source and a drain of theelement 150. The floating diffusion region FD and the source/drainregions SDR may be dopant regions doped with N-type dopants.

An interconnection structure 400 may be on the first surface 100 a ofthe substrate 100. The interconnection structure 400 may includeinterlayer insulating layers 410 and interconnections 420. In the imagesensor 1 according to at least one example embodiment of the inventiveconcepts, the light may be incident on the second surface 100 b of thesubstrate 100. The interconnection structure 400 may be on the firstsurface 100 a of the substrate 100, so photoelectric conversionefficiency of the image sensor 1 may be improved.

An anti-reflection layer 500 may be on the second surface 100 b of thesubstrate 100 to cover the device isolation pattern 200. A grid pattern510 may be between color filters CF on the anti-reflection layer 500. Inat least one example embodiment, the grid pattern 510 may be omitted.

The light-shielding pattern 520 may be at the same level as the gridpattern 510 on the anti-reflection layer 500. The light-shieldingpattern 520 may be on the second surface 100 b of the substrate 100, andthe anti-reflection layer 500 may be between the light-shielding pattern520 and the second surface 100 b. The light-shielding pattern 520 maycover the light-shielding region 120, but may not cover thelight-receiving region 110. Thus, the light incident on the secondsurface 100 b of the substrate 100 may be incident on thelight-receiving region 110, but may not be incident on thelight-shielding region 120. A material and a thickness of thelight-shielding pattern 520 may be the same as those of the grid pattern510.

The color filter CF and a micro-lens ML may be on the anti-reflectionlayer 500 of each of the active pixels AP. The color filter CF and themicro-lens ML may not be on the light-shielding region 120. The colorfilters CF may be arranged in a matrix form and may constitute a colorfilter array.

FIGS. 6A to 8A are plan views illustrating image sensors according to atleast one example embodiment of the inventive concepts. FIGS. 6B to 8Bare cross-sectional views taken along lines VI-VI′, VII-VII′, andVIII-VIII′ of FIGS. 6A to 8A, respectively. Hereinafter, thedescriptions mentioned above will be omitted or mentioned briefly toavoid duplication of explanation.

Referring to FIGS. 6A to 8A and 6B to 8B, an image sensor 2, 3, or 4 mayinclude a substrate 100 having a light-receiving region 110 and alight-shielding region 120. A plurality of active pixels AP may be inthe light-receiving region 110, and a plurality of reference pixels RPmay be in the light-shielding region 120. A shallow device isolationlayer STI, a photoelectric conversion part PD, a well region PW, afloating diffusion region FD, and source/drain regions SDR may be in thesubstrate 100 of each of the pixels AP and RP. A transfer gate TG and atleast one element 150 may be on the surface 100 a of the substrate 100of each of the pixels AP and RP. The photoelectric conversion parts PD,the well regions PW, the floating diffusion regions FD and the transfergates TG, which are in the reference pixels RP, may the substantiallysame as the photoelectric conversion parts PD, the well regions PW, thefloating diffusion regions FD, and the transfer gates TG, which are inthe active pixels AP. The photoelectric conversion parts PD may includedopants of the second conductivity type (e.g., N-type dopants). Theinterconnection structure 400 may be on the first surface 100 a of thesubstrate 100 to cover the transfer gates TG and the elements 150.

An anti-reflection layer 500, a grid pattern 510, color filters CF, andmicro-lenses ML may be on the second surface 100 b of the substrate 100.A light-shielding pattern 520 may be on the anti-reflection layer 500.The light-shielding pattern 520 may cover the light-shielding region 120but may not cover the light-receiving region 110. In at least oneexample embodiment, the grid pattern 510 may be omitted.

A device isolation region 300 may be in the light-shielding region 120of the substrate 100 to define the reference pixels RP. The deviceisolation region 300 may be a dopant region which is formed by doping aportion of the substrate 100 with dopants. The dopants of the deviceisolation region 300 may have a different conductivity type from thoseof the photoelectric conversion part PD. The device isolation region 300may define the reference pixels RP by a junction isolation technique.The device isolation region 300 may include dopants of the firstconductivity type (e.g., P-type dopants). Interface defects caused byetching may not be generated between the device isolation region 300 andthe substrate 100. Since the reference pixels RP are defined by thedevice isolation region 300, a dark current of the reference pixels RPmay be reduced and/or minimized.

A device isolation pattern 200 may include a first device isolationpattern 210 and a second device isolation pattern 220. The first andsecond device isolation patterns 210 and 220 may be in a trench 201recessed from the second surface 100 b of the substrate 100. The firstand second device isolation patterns 210 and 220 may include aninsulating material of which a refractive index is lower than that ofthe substrate 100. The first and second device isolation patterns 210and 220 may include a different material from the substrate 100, sointerfaces may be between the substrate 100 and the first and seconddevice isolation patterns 210 and 220. The first and second deviceisolation patterns 210 and 220 may include a different material from thedevice isolation region 300. The first device isolation pattern 210 maydefine the active pixels AP in the light-receiving region 110 of thesubstrate 100. In at least one example embodiment, the first deviceisolation pattern 210 may also be between the light-receiving region 110and the light-shielding region 120 to separate the light-receivingregion 110 from the light-shielding region 120.

The second device isolation pattern 220 may be in the light-shieldingregion 120 of the substrate 100. A structure, a shape, and arrangementof the second device isolation pattern 220 may be different from thoseof the first device isolation pattern 210. Hereinafter, device isolationpatterns 200 of the image sensors 2, 3 and 4 will be described in moredetail.

In at least one example embodiment illustrated in FIGS. 6A and 6B, adepth A2 of the second device isolation pattern 220 may be smaller thana depth A1 of the first device isolation pattern 210. The second deviceisolation pattern 220 may be in the device isolation region 300. In atleast one example embodiment, a bottom surface 220 b of the seconddevice isolation pattern 220 may be within the device isolation region300.

In at least one example embodiment illustrated in FIGS. 7A and 7B, awidth B2 of the second device isolation pattern 220 may be narrower thana width B1 of the first device isolation pattern 210. Here, the widthsB1 and B2 of the first and second device isolation patterns 210 and 220may be values measured at the same level. The second device isolationpattern 220 may be in the device isolation region 300. For example, asidewall 220 s of the second device isolation pattern 220 may be withinthe device isolation region 300 and may be covered by the deviceisolation region 300.

In at least one example embodiment illustrated in FIGS. 8A and 8B, adistance C2 between the device isolation patterns 200 in thelight-shielding region 120 may be greater than a distance C1 between thedevice isolation patterns 200 in the light-receiving region 110. In atleast one example embodiment, the first device isolation pattern 210 maybe between the active pixels AP to surround each of the active pixelsAP. In at least one example embodiment, the second device isolationpattern 220 may be between some of the reference pixels RP, but may notbe between others of the reference pixels RP.

In at least one example embodiment, the second device isolation patterns220 shown in FIGS. 6A, 6B, 7A, 7B, 8A, and 8B may be combined with eachother. In at least one example embodiment, the second device isolationpattern 220 may have both the depth lower than that of the first deviceisolation pattern 210 as illustrated in FIGS. 6A and 6B, and the widthnarrower than that of the first device isolation pattern 220 asillustrated in FIGS. 7A and 7B.

As illustrated in FIGS. 6B, 7B, and 8B, a total area of an interfacebetween the second device isolation pattern 220 and the substrate 100 ina unit area may be smaller than that of an interface between the firstdevice isolation pattern 210 and the substrate 100 in a unit area. Thenumber of the reference pixels RP in the unit area may be equal to thenumber of the active pixels AP in the unit area. As a result, a noisesignal caused by a dark current in the reference pixels RP may be lessthan a noise signal caused by a dark current in the active pixels AP. Inat least one example embodiment, optical characteristics of the imagesensors 2, 3 and 4 may be improved.

FIG. 9A is a plan view illustrating an image sensor according to atleast one example embodiment of the inventive concepts. FIG. 9B is across-sectional view taken along a line IX-IX′ of FIG. 9A. Hereinafter,the descriptions mentioned above will be omitted or mentioned briefly toavoid duplication of explanation.

Referring to FIGS. 9A and 9B, a substrate 100 of an image sensor 5 mayinclude a light-receiving region 110, a dummy region 115, a dummylight-shielding region 125, and a light-shielding region 120. Thelight-receiving region 110 and the light-shielding region 120 may be thesame as described with reference to FIGS. 4A, 4B, 5A, and 5B. Forexample, the light-receiving region 110 may not be covered by alight-shielding pattern 520, as illustrated in FIG. 9B. A plurality ofactive pixels AP may be in the light-receiving region 110. The activepixels AP may output electrical signals generated by incident light andnoise signals. The light-shielding region 120 may be covered by thelight-shielding pattern 520. A plurality of reference pixels RP may bein the light-shielding region 120. The reference pixel RP may output anoise signal (e.g., a reference signal).

The dummy region 115 may be between the light-receiving region 110 andthe light-shielding region 120. In more detail, the dummy region 115 maybe between the light-receiving region 110 and the dummy light-shieldingregion 125. The dummy region 115 may not covered by the light-shieldingpattern 520. Dummy pixels DP may be in the dummy region 115. The dummypixels DP may not output an electrical signal.

The dummy light-shielding region 125 may be covered by thelight-shielding pattern 520, so light may not be incident on the dummylight-shielding region 125. The light-receiving region 110 may be moreadjacent to the dummy light-shielding region 125 than to thelight-shielding region 120. A plurality of dummy reference pixels DRPmay be in the dummy light-shielding region 125. The dummy referencepixels DRP may not output an electrical signal.

In at least one example embodiment, the light-receiving region 110 maycorrespond to the core of the substrate 100 and the light-shieldingregion 120 may correspond to the edge portion of the substrate 100, asillustrated in FIG. 4A. In this case, the dummy region 115 may bebetween the light-receiving region 110 and the light-shielding region120 to surround the light-receiving region 110, and the dummylight-shielding region 125 may be between the dummy region 115 and thelight-shielding region 120 to surround the dummy region 115.

A device isolation region 300 may be in the substrate 100 of thelight-shielding region 120, the dummy light-shielding region 125 and thedummy region 115 to define the reference pixels RP, the dummy referencepixels DRP, and the dummy pixels DP. The device isolation region 300 maybe a dopant region formed by doping a portion of the substrate 100 withdopants. The device isolation region 300 may be doped with dopants of afirst conductivity type (e.g., P-type dopants).

A device isolation pattern 200 may be in a trench 201 recessed from thesecond surface 100 b of the substrate 100. The device isolation pattern200 may include an insulating material of which a refractive index islower than that of the substrate 100. The device isolation pattern 200may include a different material from the substrate 100 so an interfacemay be formed between the device isolation pattern 200 and the substrate100. The device isolation pattern 200 may define the active pixels AP inthe light-receiving region 110 of the substrate 100. The deviceisolation pattern 200 may reduce and/or prevent occurrence of crosstalkbetween the active pixels AP. The device isolation pattern 200 may alsobe between the light-receiving region 110 and the dummy region 115, andbetween the dummy region 115 and the dummy light-shielding region 125 toisolate the light-receiving region 110 from the dummy region 115 and toisolate the dummy region 115 from the dummy light-shielding region 125.In at least one example embodiment, the device isolation pattern 200 maybe further between the dummy light-shielding region 125 and thelight-shielding region 120 to isolate the dummy light-shielding region125 from the light-shielding region 120.

In at least one example embodiment, the device isolation region 300 maynot be formed in the dummy region 115, and the device isolation pattern200 may be further in the dummy region 115 to define the dummy pixelsDP. In at least one example embodiment, the device isolation region 300may not be formed in the dummy light-shielding region 125, and thedevice isolation pattern 200 may be further in the dummy light-shieldingregion 125 to define the dummy reference pixels DRP. In at least oneexample embodiment, any one of the dummy region 115 and the dummylight-shielding region 125 may be omitted.

The active pixels AP, the dummy pixels DP, the dummy reference pixelsDRP, and the reference pixels RP may have the same planar area and thesame volume, as illustrated in FIG. 9A. Referring to FIG. 9B, a shallowdevice isolation layer STI, a photoelectric conversion part PD, a wellregion PW, a floating diffusion region FD, and source/drain regions SDRmay be in each of the pixels AP, DP, DRP, and RP. A transfer gate TG andat least one element 150 may be on the first surface 100 a of thesubstrate 100 of each of the pixels AP, DP, DRP, and RP. Thephotoelectric conversion parts PD, the well regions PW, the floatingdiffusion regions FD, and the transfer gates TG of the active, dummy,dummy reference, and reference pixels AP, DP, DRP, and RP may be thesubstantially same as each other. The photoelectric conversion parts PDmay be doped with dopants of a second conductivity type (e.g., N-typedopants).

An interconnection structure 400 may cover the transfer gates TG and theelements 150 on the first surface 100 a of the substrate 100. Ananti-reflection layer 500, a grid pattern 510, the light-shieldingpattern 520, color filters CF, and micro-lenses ML may be on the secondsurface 100 b of the substrate 100.

FIG. 10A is a plan view illustrating an image sensor according to atleast one example embodiment of the inventive concepts. FIG. 10B is across-sectional view taken along a line X-X′ of FIG. 10A. Hereinafter,the descriptions mentioned above will be omitted or mentioned briefly toavoid duplication of explanation.

Referring to FIGS. 10A and 10B, a substrate 100 of an image sensor 6 mayinclude a light-receiving region 110, a dummy region 115, a dummylight-shielding region 125, and a light-shielding region 120. Thelight-receiving region 110, the dummy region 115, the dummylight-shielding region 125, and the light-shielding region 120 may bethe same as described with reference to FIGS. 9A and 9B. In otherembodiments, any one of the dummy region 115 and the dummylight-shielding region 125 may be omitted.

A device isolation region 300 may be in the substrate 100 of thelight-shielding region 120, the dummy light-shielding region 125, andthe dummy region 115 to define reference pixels RP, dummy referencepixels DRP, and the dummy pixels DP. The device isolation region 300 maybe a dopant region formed by doping a portion of the substrate 100 withdopants. A conductivity type of the dopants of the device isolationregion 300 may be different from that of dopants of a photoelectricconversion part PD. For example, the device isolation region 300 may bedoped with dopants of a first conductivity type (e.g., P-type dopants).Since the reference pixels RP are defined by the device isolation region300, a dark current of the reference pixels RP may be reduced and/orminimized.

A device isolation pattern 200 may include a first device isolationpattern 210 and a second device isolation pattern 220. The first andsecond device isolation patterns 210 and 220 may be in a trench 201recessed from the second surface 100 b of the substrate 100. The firstand second device isolation patterns 210 and 220 may include aninsulating material of which a refractive index is lower than that ofthe substrate 100. The first and second device isolation patterns 210and 220 may include a different material from the substrate 100, sointerfaces may be formed between the substrate 100 and the first andsecond device isolation patterns 210 and 220. The first device isolationpattern 210 may be in the substrate 100 of the light-receiving region110 to define the active pixels AP. The first device isolation pattern210 may also be between the light-receiving region 110 and the dummyregion 115 and between the dummy region 115 and the dummylight-shielding region 125 to separate the light-receiving region 110from the dummy region 115 and to separate the dummy region 115 from thedummy light-shielding region 125. Unlike FIGS. 10A and 10B, the firstdevice isolation pattern 210 may be further provided between the dummylight-shielding region 125 and the light-shielding region 120 toseparate the dummy light-shielding region 125 from the light-shieldingregion 120.

The second device isolation pattern 220 may be in the dummy region 115and the dummy light-shielding region 125 of the substrate 100. A shapeand arrangement of the second device isolation pattern 220 may bedifferent from those of the first device isolation pattern 210. In atleast one example embodiment, the second device isolation pattern 220may be shallower than the first device isolation pattern 210, asdescribed with reference to FIGS. 6A and 6B. In at least one exampleembodiment, the second device isolation pattern 220 may be narrower thanthe first device isolation pattern 210, as described with reference toFIGS. 7A and 7B. In at least one example embodiment, a distance betweenthe second device isolation patterns 220 may be greater than a distancebetween the first device isolation patterns 210, as described withreference to FIGS. 8A and 8B. In at least one example embodiment, thesecond device isolation pattern 210 may include a combination of atleast two of the features of the embodiments of FIGS. 6A, 6B, 7A, 7B,8A, and 8B.

In at least one example embodiment, the second device isolation pattern220 may be in one of the dummy region 115 and the dummy light-shieldingregion 125 but may not be in the other of the dummy region 115 and thedummy light-shielding region 125. In at least one example embodiment,the second device isolation pattern 220 may be further provided in thelight-shielding region 120 of the substrate 100.

The active pixels AP, the dummy pixels DP, the dummy reference pixelsDRP, and the reference pixels RP may have the same planar area and thesame volume. A shallow device isolation layer STI, a photoelectricconversion part PD, a well region PW, a floating diffusion region FD,source/drain regions SDR, a transfer gate TG, and at least one element150 may be in each of the pixels AP, DP, DRP, and RP. The photoelectricconversion parts PD, the well regions PW, the floating diffusion regionsFD, and the transfer gates TG of the active, dummy, dummy reference, andreference pixels AP, DP, DRP, and RP may be the substantially same aseach other. The photoelectric conversion parts PD may be doped withdopants of a second conductivity type (e.g., N-type dopants).

An interconnection structure 400 may cover the transfer gates TG and theelements 150 on the first surface 100 a of the substrate 100. Ananti-reflection layer 500, a grid pattern 510, a light-shielding pattern520, color filters CF, and micro-lenses ML may be on the second surface100 b of the substrate 100.

FIGS. 11A to 11D are cross-sectional views illustrating a method offorming an image sensor according to at least one example embodiment ofthe inventive concepts. Hereinafter, the descriptions mentioned abovewill be omitted or mentioned briefly to avoid duplication ofexplanation.

Referring to FIG. 11A, a substrate 100 including a light-receivingregion 110 and a light-shielding region 120 may be prepared. At thistime, a first surface of the substrate 100 may face upward. A pluralityof doping processes may be performed on the first surface 100 a of thesubstrate 100 to form a plurality of photoelectric conversion parts PD,a plurality of well regions PW, a plurality of floating diffusionregions FD, and a plurality of source/drain regions SDR in each of thelight-receiving region 110 and the light-shielding region 120. Thesubstrate 100, the photoelectric conversion parts PD, the well regionsPW, the floating diffusion regions FD, and the source/drain regions SDRmay be the same as described with reference to FIGS. 5A and 5B. Thephotoelectric conversion parts PD and the floating diffusion regions FDmay be formed by doping portions of the substrate 100 with dopants ofthe second conductivity type (e.g., N-type dopants). The well regions PWand the source/drain regions SDR may be formed by doping portions of thesubstrate 100 with dopants of the first conductivity type (e.g., P-typedopants). A doping process (e.g., an ion implantation process) usingdopants of the first conductivity type (e.g., P-type dopants) may beperformed on the first surface 100 a of the substrate 100 to form adevice isolation region 300. In at least one example embodiment, the ionimplantation process may be performed on the first surface 100 a of thesubstrate 100 of the light-shielding region 120 to form the deviceisolation region 300 defining reference pixels RP. The reference pixelsRP may be the same as described with reference to FIGS. 5A and 5B. Thedevice isolation region 300 may be formed together with the well regionsPW or the source/drain regions SDR by the same doping process. In In atleast one example embodiment, the device isolation region 300 may beformed by an additional doping process different from the doping processof forming the well regions PW and the source/drain regions SDR.

A shallow device isolation layer STI may be formed in the substrate 100to define active regions in the reference pixels RP and active pixels APto be defined. In at least one example embodiment, forming the shallowdevice isolation layer STI may include etching the first surface 100 aof the substrate 100 to form a shallow trench 140, and filling theshallow trench 140 with an insulating material. The shallow deviceisolation layer ST1 may be formed in the floating diffusion regions FDand the source/drain regions SDR.

Referring to FIG. 11B, transfer gates TG and gates of elements 150 maybe formed on the first surface 100 a of the substrate 100. A pluralityof the transfer gates TG and a plurality of the gates of the elements150 may be formed in each of the light-receiving region 110 and thelight-shielding region 120. The source/drain regions SDR may correspondto sources and drains of the elements 150. For example, the transfergate TG and at least one element 150 may be formed in each of the activeand reference pixels AP and RP. The transfer gates TG and the elements150 may be the same as described with reference to FIGS. 5A and 5B. Inat least one example embodiment, the floating diffusion regions FD andthe source/drain regions SDR may be formed after the formation of thetransfer gates TG and the gates of the elements 150. An interconnectionstructure 400 may be formed on the first surface 100 a of the substrate100. The interconnection structure 400 may include interlayer insulatinglayers 410 and interconnections 420. Thereafter, the substrate 100 maybe overturned, so a second surface 100 b of the substrate 100 may faceupward.

Referring to FIG. 11C, a mask pattern 600 may be formed on the secondsurface 100 b of the substrate 100. The mask pattern 600 may expose aportion of the substrate 100 of the light-receiving region 110 but maynot expose the substrate 100 of the light-shielding region 120. Thesecond surface 100 b of the substrate 100 exposed by the mask pattern600 may be etched to form a trench 201 in the substrate 100 of thelight-receiving region 110. A width of a top end of the trench 201 maybe greater than a width of a bottom end of the trench 201. Interfacedefects (e.g., dangling bonds) may be formed on a bottom surface and asidewall of the trench 201 during the etching process. At this time, anadditional process for removing the interface defects may not beperformed in the trench 201. In at least one example embodiment, adeposition process of forming a liner layer (not shown) and/or a dopingprocess of forming a dopant region (not shown) may be omitted. Since thedeposition process and/or the doping process is not performed, it ispossible to prevent the doped regions (e.g., the photoelectricconversion parts PD, the well regions PW, the floating diffusion regionsFD, the source/drain regions SDR, and the device isolation region 300and/or the interconnection structure 400 from being damaged. Since thesubstrate 100 of the light-shielding region 120 is not exposed duringthe etching process, the interface defects by the etching process maynot be generated in the reference pixels RP. Next, the mask pattern 600may be removed.

Referring to FIG. 11D, the trench 201 may be filled with an insulatingmaterial, so a device isolation pattern 200 may be formed in thesubstrate 100. The active pixels AP may be defined in thelight-receiving region 110 of the substrate 100 by the device isolationpattern 200. Each of the active pixels AP may include the photoelectricconversion part PD, the well region PW, the floating diffusion regionFD, and the source/drain regions SDR. At this time, the interfacedefects formed by the etching process of FIG. 11C may remain between thesubstrate 100 and the device isolation pattern 200. In otherembodiments, the device isolation pattern 200 may extend onto the secondsurface 100 b of the substrate 100 to cover the second surface 100 b.

An anti-reflection layer 500, a grid pattern 510, and a light-shieldingpattern 520 may be formed on the second surface 100 b of the substrate100. The anti-reflection layer 500, the grid pattern 510, and thelight-shielding pattern 520 may be the same as described with referenceto FIGS. 5A and 5B. The light-shielding pattern 520 and the grid pattern510 may be formed by the same process. In at least one exampleembodiment, forming the grid pattern 510 and the light-shielding pattern520 may include forming a metal layer (not shown) on the anti-reflectionlayer 500, and patterning the metal layer (not shown). In at least oneexample embodiment, the light-shielding pattern 520 may be formed by anadditional process different from the process of forming the gridpattern 510. In at least one example embodiment, the grid pattern 510may not be formed. Color filters CF and micro-lenses ML may be formed onthe anti-reflection layer 500 in the active pixels AP, respectively. Thecolor filters CF and the micro-lenses ML may be the same as describedwith reference to FIGS. 5A and 5B. An image sensor 1 may be manufacturedby the processes described above.

Since the reference pixels RP are defined by the device isolation region300, the reference pixels RP may generate reference signals from whichnoise signals caused by interface defects are removed. Thus, the noisesignals caused by the interface detects may be removed from electricalsignals of the active pixels AP by the reference signals withoutformation of the additional liner layer and/or the doped region in thetrench 201 of the light-receiving region 110. According to at least oneexample embodiment of the inventive concepts, damage of the image sensor1 may be prevented during the manufacturing processes, and opticalcharacteristics of the image sensor 1 may be improved.

In at least one example embodiment, unlike FIG. 11C, an additionaltrench may be further formed in the device isolation region 300 of thelight-shielding region 120. The additional trench may be formedsimultaneously with the trench 201 or may be formed by an etchingprocess different from the etching process of forming the trench 201.Thereafter, the additional trench may be filled with an insulatingmaterial to form one of the second device isolation patterns 220illustrated in FIGS. 6A, 6B, 7A, 7B, 8A, and 8B.

FIG. 12A is a schematic block diagram illustrating a processor-basedsystem implemented with an image sensor according to at least oneexample embodiment of the inventive concepts. FIG. 12B illustrates anelectronic device implemented with an image sensor according to at leastone example embodiment of the inventive concepts. The electronic devicemay be a digital camera or a mobile device.

Referring to FIG. 12A, a processor-based system 1000 may include animage sensor 1100, a processor 1200, a memory device 1300, a displaydevice 1400, and a system bus 1500. As illustrated in FIG. 12A, theimage sensor 1100 may capture external image information in response tocontrol signals of the processor 1200. The processor 1200 may store thecaptured image information into the memory device 1300 through thesystem bus 1500. The processor 1200 may display the image informationstored in the memory device 1300 on the display device 1400.

The system 1000 may be a computer system, a camera system, a scanner, amechanized clock system, a navigation system, a video phone, amanagement system, an auto-focus system, a tracking system, a sensingsystem, or an image stabilization system. However, the inventiveconcepts are not limited thereto. If the processor-based system 1000 isapplied to the mobile device, the system 100 may further include abattery used to supply an operating voltage to the mobile device.

FIG. 12B illustrates a mobile phone 2000 implemented with the imagesensor according to at least one example embodiment of the inventiveconcepts. In at least one example embodiment, the image sensor may beapplied to a smart phone, a personal digital assistant (PDA), a portablemultimedia player (PMP), a digital multimedia broadcast (DMB) device, aglobal positioning system (GPS) device, a handled gaming console, aportable computer, a web tablet, a wireless phone, a digital musicplayer, a memory card, and/or other electronic products transmittingand/or receiving information by wireless.

According to at least one example embodiment of the inventive concepts,the active pixels may be defined by the device isolation pattern, andthus, the crosstalk between the active pixels may be prevented. Inaddition, the reference pixels may be defined by the device isolationregion, and thus, the interface defects may not be generated between thedevice isolation region and the substrate. In other words, the referencepixels may generate electrical signals which have reduced noise signalsor do not have the noise signals. The electrical signals generated fromthe reference pixels may be used as the reference signals, so the imagesensor may output the photoelectric signals from which the noise signalscaused by the dark current are removed. As a result, the opticalcharacteristics of the image sensor may be improved.

While the inventive concepts have been described with reference toexample embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirits and scopes of the inventive concepts. Therefore, itshould be understood that the above embodiments are not limiting, butillustrative. Thus, the scopes of the inventive concepts are to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing description.

1. (canceled)
 2. An image sensor comprising: a substrate having a firstsurface and a second surface opposite to the first surface; a pluralityof photoelectric conversion parts disposed between the first and secondsurfaces; a plurality of interconnection structures disposed on thefirst surface; a light shielding pattern disposed on the second surfaceof the substrate; a first trench recessed from the second surface of thesubstrate overlapping the light shielding pattern; a second trenchrecessed from the second surface of the substrate and not overlappingthe light shielding pattern; a first device isolation pattern disposedin the first trench; and a second device isolation pattern disposed inthe second trench, wherein a depth of the first device isolation patternis smaller than a depth of the second device isolation pattern.
 3. Theimage sensor of claim 2, further comprising a third trench disposedbetween the first trench and the second trench, the third trench havinga substantially same height with the second trench, and the third trenchbeing positioned at or near a first end of the light shielding pattern.4. The image sensor of claim 2, further comprising a p-type dopingregion under the first surface of the substrate.
 5. The image sensor ofclaim 4, wherein the second trench contacts the p-type doping region. 6.The image sensor of claim 2, further comprising an anti-reflection layerdisposed between the light shielding pattern and the second surface ofthe substrate.
 7. The image sensor of claim 2, the first and seconddevice isolation patterns comprise insulating material.
 8. The imagesensor of claim 7, wherein the insulating material has a refractiveindex lower than a refractive index of the substrate.
 9. The imagesensor of claim 2, wherein the first trench is formed in a lightshielding region, the second trench is formed in a light receivingregion, and a third trench is formed in a dummy region, wherein eachfirst, second, and third trench is disposed between the plurality ofphotoelectric conversion parts.